Method and device for processing an image in order to construct from a source image a target image with charge of perspective
First Claim
1. A method of processing images for constructing a digitized target image from a digitized source image having a fixed frame line, and including pixels each having a digital signal value, said source and target images having substantially common view points, said method comprising the steps:
- (a) determining a fixed set of orthonormal reference axes originating at said common view point;
(b) generating a fictive spherical surface centered at the common view point, provided with pixels at a predetermined resolution;
(c) generating an address for each pixel on said spherical surface, associated with a couple of spherical coordinates, constituted of orientation angles, with respect to said set of orthonormal reference axes, of a fictive straight light ray passing through said common view point and through said pixel of the spherical surface;
(d) calculating, for each spherical coordinates couple, a corresponding address of a point situated at the intersection of the source image and of the corresponding fictive straight light ray, by using a direct perspective trigonometrical transform;
(e) storing the address of said corresponding point of the source image at the address of said pixel of the fictive spherical surface associated with said spherical coordinates couple;
(f) generating an address for each pixel of the target image;
(g) calculating, on the basis of the address of a pixel, called the initial pixel, in the target image, approximate orientation angles, with respect to said fixed set of orthonormal reference axes, of an actual straight light ray passing through said initial pixel and said common view point, by using an inverse perspective linear transform;
(h) determining an address of a point in the source image, by matching at best the approximate orientation angles related to said initial pixel with a stored spherical coordinates couple;
(I) calculating a function characteristic of the digital signal value at said point in said source image and assigning said value to said initial pixel in said target image; and
(j) repeating steps (g) to (I) for each pixel of the target image.
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Abstract
A method of processing a digital image in order to construct a calculated image, termed the target image (I*), which represents a so-called source image (I) reconstructed with modifications to the tilting angle, panning angle and scale factor in relation to this source image. This method includes determining a common view point (P), for the source image (I) and the target image (I*), as the origin of an orthonormal reference frame; and calculating, for every pixel (M*) with address (X*, Y*) in the target image (I*), spherical coordinates (α, β) by a linear function G-1 such that (α, β)=G-1 (X*Y*), the coefficients being functions of the modified tilting and panning angles and scale factor. Finally, the method includes reading a pair (X, Y) which is stored in a table and which constitutes the address of a point (M), in the source image (I), corresponding to the pixel (M*) in the target image (I*), by the matching, to the resolution of the table, the spherical coordinates (α, β) with one of the addresses (αo, βo) of the table.
96 Citations
20 Claims
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1. A method of processing images for constructing a digitized target image from a digitized source image having a fixed frame line, and including pixels each having a digital signal value, said source and target images having substantially common view points, said method comprising the steps:
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(a) determining a fixed set of orthonormal reference axes originating at said common view point; (b) generating a fictive spherical surface centered at the common view point, provided with pixels at a predetermined resolution; (c) generating an address for each pixel on said spherical surface, associated with a couple of spherical coordinates, constituted of orientation angles, with respect to said set of orthonormal reference axes, of a fictive straight light ray passing through said common view point and through said pixel of the spherical surface; (d) calculating, for each spherical coordinates couple, a corresponding address of a point situated at the intersection of the source image and of the corresponding fictive straight light ray, by using a direct perspective trigonometrical transform; (e) storing the address of said corresponding point of the source image at the address of said pixel of the fictive spherical surface associated with said spherical coordinates couple; (f) generating an address for each pixel of the target image; (g) calculating, on the basis of the address of a pixel, called the initial pixel, in the target image, approximate orientation angles, with respect to said fixed set of orthonormal reference axes, of an actual straight light ray passing through said initial pixel and said common view point, by using an inverse perspective linear transform; (h) determining an address of a point in the source image, by matching at best the approximate orientation angles related to said initial pixel with a stored spherical coordinates couple; (I) calculating a function characteristic of the digital signal value at said point in said source image and assigning said value to said initial pixel in said target image; and (j) repeating steps (g) to (I) for each pixel of the target image. - View Dependent Claims (2, 3, 4)
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5. A method of processing images for constructing a digitized target image from n adjacent digitized images having a fixed frame line and referred to as source images, the pixels of the source images having digital signal values, and said source and target images having substantially common view points, comprising:
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(a'"'"') determining a fixed set of orthonormal reference axes originated at said common view point; (b'"'"') generating a fictive spherical surface centered at the common view point, provided with pixels at a predetermined resolution; (c'"'"') generating an address for each pixel on said spherical surface, associated with a couple of spherical coordinates, constituted of orientation angles, with respect to said set of orthonormal reference axes, of a fictive straight light ray passing through said common view point and through said pixel of the spherical surface; (d'"'"') calculating, for each spherical coordinates couple, a corresponding address of a point situated at the intersection of one of the source images and of the corresponding fictive straight light ray, by using a direct perspective trigonometrical transform; (e'"'"') storing the address of a corresponding point of said particular source image, associated with an index indicating the particular source image out of the n source images that the fictive straight light ray intersects, at the address of said pixel of the fictive spherical surface associated with said spherical coordinates couples; (f'"'"') generating an address for each pixel of the target image; (g'"'"') calculating, on the basis of the address of a pixel called initial pixel in the target image, approximate orientation angles, with respect to said fixed set of orthonormal reference axes, of an actual straight light ray passing through said initial pixel and said common view point, by using an inverse perspective linear transform; (h'"'"') determining an address of a point in a source image, and an index indicating the particular source image where said point lies, by matching at best the approximate orientation angles related to said initial pixel with a store spherical coordinates couple; (I'"'"') calculating a function characteristic of the digital signal value at said point in said particular source image and assigning said value to said initial pixel in said target image; and (j'"'"') repeating steps (g'"'"') to (j'"'"') for each pixel of the target image. - View Dependent Claims (6, 7, 8, 9)
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10. An image processing device comprising:
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a system of n fixed real cameras, n being an integer greater than 0, said real cameras being arranged such that their individual fields of view merge so as to form a single wide angle field of view for observation of a panoramic scene, said real cameras providing adjacent images referred to as source images; an image construction system simulating a mobile virtual camera continuously scanning the panoramic scene so as to form a sub-image referred to as a target image corresponding to a selected section of a wide-angle field of view, and constructed from said source images; means for digitizing said source and target images such that each pixel corresponds to a digital signal value; calibration means for determining a substantially common view point to said source and target images, and a fixed set of orthonormal reference axes originated at said common view point; an address generator for generating, pixel by pixel, respective addresses for the pixels of the target image; an address computer including; tabulation means for storing addresses of pixels provided on a fictive spherical surface, centered at the common view point, said pixels being disposed at a predetermined resolution, each of said addresses being associated with a couple of spherical coordinates constituted by orientation angles, defined with respect to said fixed set of orthonormal reference axes, of a fictive straight light ray passing through said common view point and through said pixel at the corresponding address of the fictive spherical surface, and each couple of spherical coordinates being associated with an index indicating a particular source image out of the n source images that the fictive straight light ray intersects, and being associated with an address of a corresponding point of said particular source image; calculation means for calculating, on the basis of the address of a pixel called initial pixel in the target image, approximate orientation angles, with respect to said fixed set of orthonormal reference axes, of an actual straight light ray passing through said initial pixel and said common view point, by using an inverse perspective linear transform system; addressing means for determining, from the tabulation means, an address of a point in a source image, and an index indicating the particular source image where said point lies, by matching at best the approximate orientation angles related to said initial pixel with a stored spherical coordinates couple; calculation means for calculating a function characteristic of the digital signal value at said point in said particular source image; and means for assigning said value to said initial pixel in said target image. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification